i have a 1986 s-10.it's 2.6 five speed[straight].When i move the lever backword ,the 4-w light is illuminated and the transmission makes a new whining sound, as if the transfer case is engaged,but neither front wheel will pull[spin, when i am stuck]'wonder what the most likely failure would be.thnks for any ideas guys.
Ty

 

The most common failure is the vacuum lines. Make sure tehy are in good shape. There are three vacuum lines that run down to the t-case. One provides vacuum tot he switch, one provides vacuum from the t-case switch to the axle vacuum control module next to the battery, and the last one is a vent line and spilts off and attaches tot eh t-case in a seperate place besides the 3 hose fiting.

Make sure the vacuum actualtor is working. Unplug the vacuum line and move the diaphram with your finger. Place your thumb over the vacuum hose hole and see if the diaframe holds. If not, leak. Replace or install a Posi-Lok kit.